1. Technical Field
This disclosure relates to noise suppression. In particular, this disclosure relates to reducing low-frequency noise in speech signals.
2. Related Art
Users access various systems to transmit or process speech signals in a vehicle. Such systems may include cellular telephones, hands-free systems, transcribers, recording devices and voice recognition systems.
The speech signal includes many forms of background noise, including low-frequency noise, which may be present in a vehicle. The background noise may be caused by wind, rain, engine noise, road noise, vibration, blower fans, windshield wipers and other sources. The background noise tends to corrupt the speech signal. The background noise, especially low-frequency noise, decreases the intelligibility of the speech signal.
Some systems attempt to minimize background noise using fixed filters, such as analog high-pass filters. Other systems attempt to selectively attenuate specific frequency bands. The fixed filters may indiscriminately eliminate desired signal content, and may not adapt to changing amplitude levels. There is a need for a system that reduces low-frequency noise in speech signals in a vehicle.